In last night's 10-4 victory over the Tigers, Rangers starter Yu Darvish threw 130 pitches. In his previous start, Darvish threw 105 pitches. Six days before that, in a start against the Red Sox, he threw 127 pitches. Should we be freaking out about how many pitches Darvish is throwing?

Last year, Ben Lindbergh of Baseball Prospectus talked pitcher workloads with Glenn Fleisig of the American Sports Medicine Institute—one of the world's foremost authorities on biomechanics—and an anonymous MLB scouting executive. The entire interview is republished here, with permission.

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Ben Lindbergh: So you mentioned the more innings or the more pitches, the more stress, but obviously I’m sure there’s a lot more that goes into it. Is it just total innings or total pitches? How much does stress play into it, or rest between outings?

Glenn Fleisig: Trying to keep things simple, our science and our medicine here at ASMI has shown some things. It’s not just the velocity, but the pitcher with better mechanics and sharing the load more with the whole body, whereas the pitcher with worse mechanics is putting a bigger share of the load on your elbow or shoulder. So not all 90-mph fastballs are the same. A 90-mph fastball with proper mechanics is less stressful on the elbow and shoulder, so mechanics is definitely one factor.

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The other thing is—this is a big concept that people are overlooking—the arm, the elbow, the shoulder of any of these pitchers—these are living people, they’re not pieces of metal or plastic or whatever. So you can’t just count things up. In other words, you’ve heard the analogy: people say ‘You have so many bullets, and you don’t shoot all your bullets,’ you shouldn’t always just blow it on one game or season or this or this or that. That analogy works with bullets, because if you had a case of bullets and you shot them all, you would be out. But an arm, or pitches in an arm, is not a proper analogy, because a pitcher doesn’t have a certain number of throws in his arm. That’s true because pitchers are living, breathing, and their arm is repairing. The arm is breaking down and repairing.

So in other words, for example, a thousand pitches over a season would not be the same as a thousand pitches over two days. A thousand bullets over a season and a thousand bullets over two days would be the same number of bullets. You can’t just count it up, because what happens is, when you pitch a game, you throw 70 pitches in a game or 120 pitches in a game, you have little damage in your elbow and shoulder. So the guys who don’t get hurt, like everybody else, they get little damage in their elbow and shoulder every time they pitch, but they are doing a good job of not getting excessive damage on any one particular day. In other words, when their arm gets to the point of being fatigued, they’re not going past that point. Either for whatever reason they haven’t reached that point or for whatever reason they come out of the game at that point. What happens is, you pitch a game as a starting pitcher or, frankly, if you and I worked out or rode our bikes or did something where you feel like your muscles are fatigued, and then you don’t pitch for the next few days, a big part of the secret is how much damage you did to your arm, which has to do with mechanics and pitch count, but the other part of it is what you do on your recovery days.

Recovery days, a pitcher who doesn’t get hurt, any of these guys you’re talking about, have a pattern where they pitch, and then they have sufficient rest and recovery before the next time they pitch. A guy who blows out his arm, elbow or shoulder, doesn’t blow it out from one day. What it is—he went through a season, or more seasons, where he pitched a little or pitched on a given day, and then he had recovery days and he pitched again, but he was never quite recovering each time, and his damage from game after game accumulated and became an injury. The guys you’re talking about, what’s happening is they pitch, and then they do the right steps to recover completely, and then they’re ready to pitch again, essentially like a clean slate each game, ready to start with a healthy arm.

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BL: So does that make the concept of an innings limit a little too reductive, do you think? I mean, could a guy theoretically pitch any number of innings as long as he’s properly managed?

GF: Yes. You’re correct. There’s pitch count limits or innings limits—for instance, doing the research that Dr. [James] Andrews and myself did, pitch count became part of Little League, but even though I’m essentially the reason why there’s pitch counts in Little League, I can tell you, in an ideal world, there should be no pitch count rules or limits. And while that might be surprising for the guy who did the science studying that, that’s because, in an ideal world, pitchers and coaches should use pitch counts as guidelines to say where are you if you feel where your arm is. But the pitch counts shouldn’t be rules, they should be guidelines to give you a feel for if he has had a high workload or not.

The rule should be that when a pitcher has arm fatigue, he should come out. So when he has arm fatigue, he should not pitch again until the fatigue is gone. The reason that in youth baseball, like Little League, we have pitch count rules, is because in that society, in that world, you have volunteer coaches with good intentions—the dads, and everything—but they’re not experts on this. And so they’re not experts in judging and deciding what’s too much for their kids. So we have that rule in Little League and youth baseball because it’s the second best choice. The best choice is to have expert coaches at every team who are making objective decisions, but you can’t mandate that, so we have pitch count rules. Now major-league baseball is a different situation. You have professional coaches, professional trainers, and you have a lot of vested interest. If a multi-million-dollar pitcher blows out his arm, or a few of them, that coach, pitching coach or trainer would feel their job is on the line. So they certainly have a vested interest in keeping their guys healthy.

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BL: So without commenting on any specific team or pitcher, would you say that a team that puts hard innings limits in place is just sort of going overboard with risk aversion or covering their own ass? I mean, I’m sure they must base it on some sort of research, but maybe they’re not looking at the right research.

GF: Yeah. I do say that. If a major-league team or minor-league team has a hard pitch count across their whole organization, they can do better than that. They should be using—because they have professional coaches throughout their major and minor leagues, and a professional medical staff—they should be using pitch counts as a feel, as a guideline for who has pitched a lot, who hasn’t pitched a lot, and then they should individualize it and know each of their pitchers, each of their athletes, and know who is a quick responder, who’s doing well on the physical assessments with the trainers and medical staff, who has good mechanics according to the pitching coach, things like that. And they should individualize it and they should say, ‘Oh, Rodriguez, he recovers quickly, but Johnson, he’s always in pain, so let’s keep Johnson lower than Rodriguez,’ and individualize it.

Plus, even within a person—even if they say, ‘Rodriguez, he seems to be healthy and doing well and good mechanics and very fluid and in good shape, all those things,’ they shouldn’t set a pitch count number for him; they should set a soft pitch count number—‘He can go to this level, 100 pitches or whatever”—but then game by game, they should monitor and take him out when he’s giving signs of being fatigued or if there’s a history of he’s been pitching a lot recently, or he’s stinking tonight, other things where you individualize it. But a hard pitch count is really for youth baseball and perhaps high school baseball, when you can’t assume the coaches are all experts.

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Ben Lindbergh: How do you evaluate a guy’s workload? Do you look at total innings, or total pitches, or high-stress innings, or time between starts or outings, or…?

MLB scouting executive: I think innings is first and foremost in what you look at, if only because it’s sort of built into our profile of a pitcher. We have certain expectations for every spot in the rotation. So what your ideal no. 1 starter’s profile looks like is going to be different from what your no. 5 starter looks like. Along with that, the idea is those top-of-the line starters are usually guys who can give you 200-plus innings. So that’s kind of where innings come from, because if you slice it up too finely, it becomes very difficult. You say, ‘Well, you know, we expect him to throw 90 pitches per outing, or 12 pitches per inning,’ it’s not something that’s very easy to break down and project, if that makes any sense.

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And at the same time, it’s very difficult to get information about bullpen usage. You know, how many warm-up tosses you’ve thrown in the bullpen, or stuff like that. So I think innings is just kind of the benchmark. That being said, better is the enemy of good enough, so if there’s a method that comes along that we think ‘Hey, this works better,’ I think the baseball industry is becoming quicker to approach more radical approaches. But I think in terms of stress, I think you can look at things like innings first of all, just to kind of project what you can expect reasonably. You know, you’re not going to take a guy who threw 100 innings last year and expect him to throw 180 the next year out.

So you want to look for guys who, for the bullpen, if you see numbers like, you look at 60 innings, and you go, ‘Oh, that’s not too bad,’ but then you look like, ‘Geez, 80-plus games, he’s pitching every other day, more than that.’ And if you’re pitching every day, that means you’re throwing… if you’re coming out of the pen every day, that means you’re throwing pitches in the pen that aren’t getting tallied up. There might be some games where you have to get hot, and then you sit down and get hot again, so that’s, I think, when you’re talking relievers, that games column becomes a little more important, sort of tracking appearances and trying to create some sort of link between appearances and innings pitched is a good way of looking at fatigue.

Now, I’m not particularly well versed in this, but I know that with PITCHf/x, you can look at arm angles and arm slots and release points, and say, ‘This guy’s release point is down.’ You can look at, obviously, velocity of pitches is pretty much a no-brainer. But there are some little indicators also that can indicate fatigue even as games go on. As an individual game, you can say, well, it looks like he’s starting to tire because his arm slot got lower. Is that 100 percent? Maybe he’s just trying to give hitters a different look, who knows. There’s such a fine sample that it can become difficult. You don’t want to go looking for ghosts, as it were.

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BL: So does it make sense to come up a single, specific number that it’s dangerous for a guy to go beyond, or is it too reductive or too simplistic to do that, since so much depends on what a guy does between starts? Can a guy pitch indefinitely as long as he takes the proper care between starts, or is there a number at which you just say the risk outweighs the benefits?

Exec: I think it goes back to everybody being a unique case, because everybody’s bodies do work differently. Ideally, you want to get a sense of how much a guy can take. Twenty-five starts is a universal. Twenty-five starts is about 180 innings. For one guy, that can be a lot, for another guy, that might not be very much at all. I wish there was a magic number. But I think beyond the ‘Verducci Effect’-type philosophy, and if it’s not exactly his, whatever his number is, 15 innings, or 20 innings, that sort of concept of not wanting somebody to take too big of a jump, makes sense. At the same time, I think what I’m hearing from our guys at the minor-league levels, especially younger pitchers, you know, short-season ball, these guys are on very strict pitch counts. So these innings, even at the lower levels, are kind of artificial. Your innings are what they are because of your pitch count. That’s a different way of looking at things.

BL: So how do you determine how a guy responds between starts? I mean, are you relying on a pitcher being honest and telling you, ‘Hey, I’m a little sore today,’ or are you just looking at his results and seeing if he’s lost some stuff? How much does it depend on their actually disclosing their status to someone?

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Exec: Right. I mean, I always kind of operate under the notion that, above all else, these guys are super competitive. They’re all just, this is what they do for a living. If you ask a guy how he feels, and if he thinks that there’s any chance it’s going to affect his ability to play, he’s going to tell you he feels good. Obviously, everybody is different, but as a baseline, it’s very difficult to tell you, ‘Oh, you know, I’m banged up, take me out.’ They’re going to tell you they’re fine, they’re going to tell you they feel great. And that’s what they should do, that’s their prerogative. It’s the job of, I think, the pitching coach and the bullpen coach first and foremost, because basically they’ve been living with these guys since early February. They know what the deliveries look like, they know how these guys land, it’s their job to get a sense for when the mechanics are right and when things don’t look right. And that’s also when you bring in your trainers, and what they see, and the treatment they can give.

The honest truth is that with everything it takes to get to the major-league level, by the time you get here, everybody’s got some type of damage. Nobody’s going to—if you give somebody an MRI on their elbow or their shoulder, you’re going to find something. It’s not a question of ‘Is there damage?’, but of just, how do you monitor it? Pitching is going to break your body down, it’s going to break an arm down. But I think it’s really the pitching coach and the trainers who are watching these guys on a daily basis who are going to be ahead of the ball. If a guy’s hurting, it’s going to show up in the data down the line—I always think of data as mechanics plus time, but when the mechanics go to shit, it’s going to be maybe five starts before the data is meaningful enough. But if the pitching coach, the trainers are right there, then boom, as soon as something goes wrong, they’re going to see it. So they’re sort of the first responders there, and you’ve got a better chance of treating it—it’s like they say, prevention is better than a cure. If you see it right away and you prevent it, that’s great. You don’t want to be dealing with it once a problem pops up.